Irritable Bowel Syndrome (IBS) has a major impact on the healthcare system in that IBS management in the U.S. is estimated to cost 8 billion dollars annually in direct medical care costs and as high as 25 billion dollars in indirect economic costs.
Compounds which alter the activity of certain serotonin receptors have shown benefit for the symptomatic treatment of IBS. To that end, the only U.S. drug in this class is alosetron, a serotonin type-3 (5-HT3) receptor antagonist. Shortly following its introduction in 2000, alosetron was withdrawn from the market due to instances of ischemic colitis occurring in IBS patients. Later, the drug was reinstated by the FDA because the demand by patients was so great for a treatment for IBS. In 2002, the US Food and Drug Administration approved alosetron hydrochloride (LOTRONEX®) tablets under restricted conditions for patients in whom the medical benefits outweigh the risks.
Ramosetron, a 5-HT3 receptor antagonist originally developed and marketed for emesis associated with cancer therapy, was approved in Japan for the treatment of IBS. Since its introduction in 2008 no reports of ischemic colitis have appeared.
5-HT3 receptor modulators with improved safety profiles are therefore highly desired for the treatment of IBS. A 5-HT3 receptor modulator is an agent which can either inhibit (e.g., an antagonist) or partially activate (e.g., a partial agonist) the 5-HT3 receptor.
Nausea and vomiting caused by chemotherapy remain among the most distressing side effects for patients undergoing treatment for cancer. Depending upon the chemotherapy agents or regimens given, up to 90% of patients may suffer from some form of chemotherapy-induced nausea and vomiting (CINV). Symptoms from CINV can be severely debilitating and often result in patients refusing further courses of chemotherapy, with obviously unfavorable consequences as regards to progression of the cancer. Furthermore, CINV is burdensome on the medical system, consuming time from the healthcare staff, who could otherwise attend to other patients or medical issues.
CINV is divided into two main categories: acute CINV and delayed CINV. Acute CINV occurs within the first 24 hours of treatment; delayed CINV occurs from 24 hours to 120 hours following treatment. Delayed CINV remains a highly under treated side effect in patients undergoing chemotherapy, as healthcare providers tend to underestimate the number of patients who suffer from delayed CINV. Furthermore, delayed CINV greatly impairs patients' ability to provide care to themselves once they have been discharged.
Compounds that target 5-HT3 receptors are effective anti-emetics; they constitute the single greatest advance in the management of nausea and vomiting in patients with cancer. Blocking the 5-HT3 receptor signal in the CNS or periphery appears to prevent acute emesis. 5-HT3 receptor modulators are approved to prevent acute CINV. Palonosetron is also approved for the prevention of delayed CINV. In addition, the combination of the neurokinin antagonist aprepitant (EMEND®), a 5-HT3 receptor modulator, and the corticosteroid dexamethasone has been shown to be highly effective in preventing both acute and delayed cisplatin-induced emesis.
Palonosetron has received approval for the treatment of post operative nausea and vomiting (PONV). Therefore, 5-HT3 receptor modulators may be useful for the treatment of PONV.
Clearly, there is a need for improved therapy for IBS, CINV, and PONV. The present invention is directed to achieving this objective.